Seattle-based USNC's Pylon microreactor is a containerised system capable of producing 1-5 MWe for up to three years. It has a lower mass than the company's Micro Modular Reactor (known as MMR) high-temperature gas-cooled reactor system. The system is designed to be easily transportable to off-grid locations both on Earth and in space: for terrestrial use, the system comprises separate nuclear heat supply system and balance-of-plant modules, each individually fitting within a standard 20-foot (6-metre) container.

PTT, based in Wiscasset, Maine, was formed in April 2012 and is focused on the development and deployment of advanced supercritical carbon dioxide (sCO2) turbine power generation, energy storage and propulsion systems.

In July last year, the company announced it had established a new subsidiary, PTT Nuclear Energy Systems, after it had "identified significant potential and opportunity for its breakthrough energy conversion technologies in the accelerating VSMR (very small modular reactor) and MMR (micro modular reactor) programmes (350 Kw – 10 MW), and a clear intermediate-term opportunity in the SMR (small modular reactor) 30 MW to 100 MW class range". At the time, PTT said it was "working to field a family of its proprietary modular sCO2 energy conversions systems with initial capabilities ranging from 350Kw to 10 MW".